/Engine/Source/Editor/UnrealEd/Classes/Editor/EditorEngine.h
Convenience method for adding a Slate modal window that is parented to the main frame (if it exists) This function does not return until the modal window is closed.
void EditorAddModalWindow ( [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWindow](API\Runtime\SlateCore\Widgets\SWindow) > InModalWindow ) const